Control surfaces are known in the art. To date, rigid doors have been used as control surfaces to control air flow within a housing of a heating, ventilation, and air conditioning unit (HVAC). Recently, composite structures have been designed to replace these conventional rigid doors. Specifically, the composite structures have been designed as flexible films. The film controls airflow by opening and closing apertures in inlets and outlets of the housing of the HVAC system. Generally, the film is disposed in a film valve assembly that includes a frame having rollers. To control air flow, an actuator moves a first roller to wind and unwind the film. As the film is wound and unwound, the openings in the film align with the apertures in the housing, thus allowing air to flow through the housing.
Prior art control surfaces, such as rigid doors, are well known to those skilled in the art and include substrates including filled polypropylene or nylon plastic covered by a semi-open or open cell foam, or an overmolded rubber. The disadvantages of using these control surfaces include a need for additional packaging volume within the HVAC system and the separation of hot and cold air streams resulting in decreased air mixing efficiency.
Additionally, prior art control surfaces such as films are also well known to those skilled in the art and include both elastomeric and non-elastomeric layers disposed on substrates including fabrics and polymers. Yet, in every case, the prior art films do not sufficiently perform when tested in the housing of the HVAC system. Common disadvantages of prior art films include accumulation of static charge, high coefficients of friction, film blocking, film creep, high bending resistance, lack of noise reduction, and tacky surfaces.
Specifically, accumulation of static charge causes airborne debris to attach to surfaces of the film resulting in noise production as the film is moved within the housing of the HVAC system. High coefficients of friction require the film valve assembly to be equipped with larger actuators to overcome the possibility that the film will stick, slip, or get stuck in one position. Film blocking results in noise production as the film is separated from itself as the film is unwound from the rollers. Film creep results in stretching that leads to the misalignment of the film within the housing of the HVAC system. High bending resistance requires the film valve assembly to be equipped with larger actuators to overcome the possibility that the film will not efficiently wind onto the rollers. A lack of noise reduction is caused by the excessive vibration of the film when disposed in the film valve assembly, resulting in unacceptable noise levels within the housing of the HVAC system. Finally, tacky surfaces result in the generation of peeling noises as the film breaks contact with the rollers.
Theoretically, many different composite structures could be used as films in the housing of the HVAC system. One such composite structure is disclosed in U.S. Pat. No. 5,217,797 to Knox, et al. This patent discloses a composite structure that includes a substrate including perfluoropolymer fibers sandwiched between a perfluoropolymer layer and an elastomeric layer. Further, the substrate can be reinforced by glass, quartz, aramid, or nylon fiber. Yet, this patent does not disclose a silicone topcoat layer disposed on an elastomeric layer.
Yet, the composite structure disclosed in U.S. Pat. No. 5,217,797 is not the sole prior art. Other attempts have been made to produce films or composite structures that overcome all of the aforementioned disadvantages. Such attempts include a composite structure for use in the housing of the HVAC system described in European Patent 0 705 725 A1 to Higashihara of Denso, formerly Nippondenso Co. Ltd. of Aichi-ken, Japan. This patent discloses a composite structure including seven layers. More specifically, the patent discloses a composite structure including a polyphenylene sulfide layer and an adhesive epoxy layer disposed on both sides of the polyphenylene sulfide layer. The polyphenylene sulfide layer and the adhesive epoxy layer are sandwiched between two nylon layers. The two nylon layers are further sandwiched between two layers of silicone.
The composite structure described in European Patent 0 705 725 A1 is further described in a 1996 SAE article 960687 entitled “Development of a Film Door Type Air Conditioning Unit.” This article discloses the inability of a silicone film alone to adequately reduce noise in the housing of the HVAC system.
Additionally, a composite structure of a very similar but slightly different design to the European Patent 0 705 725 A1 by Denso was also tested. The composite structure is used by Lexus, a division of The Toyota Motor Company of Toyota City, Japan, as a film in the housing of the HVAC system designed by Denso for the 1995 Lexus LS400. This composite structure includes a polyphenylene sulfide layer and a binder layer including alumina trihydrate disposed on both faces of the polyphenylene sulfide layer. The polyphenylene sulfide layer and the alumina trihydrate binder layers are sandwiched between two nylon layers. The two nylon layers are further sandwiched between two layers of silicone.
Several of the Lexus HVAC systems and the corresponding composite structures were removed from used automobiles and analyzed. The analyses showed that the aforementioned composite structures yielded unsatisfactory results due to excessive nylon fraying. It is known to those skilled in the art that non-coated fibers will fray. In the tested HVAC systems and the corresponding composite structures, the excessive nylon fraying resulted from an incomplete sandwiching of the two nylon layers with the two layers of silicone. Specifically, the incomplete sandwiching resulted from the two layers of silicone disposed only on a top edge of the two nylon layers, as opposed to being fully disposed entirely over the two nylon layers. The incomplete sandwiching caused the nylon layers to wear. The frayed nylon became intertwined with the rollers of the film valve assemblies, thus reducing the ability of the composite structures to freely move and rendering the composite structures unusable.
Additionally, the analyses showed that the aforementioned composite structures yielded unsatisfactory results due to excessive nylon freezing. Specifically, if the evaporator core produces condensation, the nylon-fibers will absorb the condensation. Once the nylon-fibers absorb the condensation, the nylon-fibers will freeze in low temperatures, and increase in stiffness. The increase in stiffness will render the nylon-fiber unusable.
Additionally, component level debris intrusion testing of the composite structures showed that airborne debris was embedded in surfaces of the composite structures. The airborne debris resulted in the generation of noise as the composite structures were moved in the housing of the HVAC systems.
In another attempt to develop a composite structure that overcomes the aforementioned disadvantages of prior art control surfaces, Nippondenso Co. Ltd. of Aichi-ken, Japan developed a film disclosed in U.S. Pat. No. 5,326,315. This patent discloses a film that includes at least two kinds of layers having different characteristics, for example, a film layer provided on at least one side of a cloth layer, or a resin material disposed on one side of the cloth layer. That is, two different kinds of layers are provided such as a film layer and a fabric layer, or a resin layer and a fabric layer.
Specifically, the film includes six embodiments. In a first embodiment, the film includes a resin film layer, a cloth layer disposed on the resin film layer, and a resin coat layer disposed on the cloth layer. In a second embodiment, the film includes the resin film layer and the cloth layer. The cloth layer is disposed on the resin film layer with an adhesive. In a third embodiment, the film includes the resin film layer and the cloth layer. The cloth layer is disposed on the resin film layer with the adhesive, and the resin coat layer is impregnated in the cloth layer. In a fourth embodiment the film includes the cloth layer and the resin film layer. The resin film layer is disposed on the cloth layer with the adhesive. In a fifth embodiment, the film includes the cloth layer and the resin coat layer. The resin coat layer is impregnated in the cloth layer. In the sixth embodiment, the film includes the cloth layers disposed on the resin film layer with the adhesive. Additionally, in the sixth embodiment, the resin film layer is disposed on the cloth layer with the adhesive.
The resin film layer includes PPS (polyphenylene sulfide), PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PEI (polyether imido), PI (polyimido), PES (polyether sulfone), PEEK (polyether etherketone), PSF (polysulfone), PC (polycarbonate), PVC (polyvinyl chloride), and PS (polysulfone).
The cloth layer can include filaments of nylon fibers, PET fibers, PPS fibers, aramid fibers, p-aramid fibers, novoloid fibers, polytetrafluoroethylene fibers, glass fibers, carbon fibers, and boron fibers. Also, the resin coat layer includes silicon resin, acrylic resin, or fluorocarbon resin.
The film disclosed in this patent does not include a silicone topcoat layer disposed over an elastomeric layer. Therefore, if this film is used as the film in the housing of an HVAC system, the absence of the elastomeric layer allows for excess vibration leading to excessive noise generation, and thus not improving on the aforementioned disadvantages.
In another attempt to develop a composite structure that overcomes the aforementioned disadvantages of prior art control surfaces, Milliken & Company of Spartanburg, S.C. developed a film disclosed in International Patent WO 01/70529 A1. This patent discloses a film including a synthetic, continuous, multi filament, non-textured yarn layer with improved dimensional stability & creep resistance. Further, the patent discloses the yarn's floats reducing the coefficient of friction of the film and the noise generated when the film moves in the housing of the HVAC system. Still further, the application discloses the use of a polyurethane and/or polyacrylate layer disposed on the yarn layer that reduces fray resistance as the film moves in the housing of the HVAC system. Yet, this patent does not disclose a silicone topcoat layer disposed on an elastomeric layer.
When tested, the Milliken film yields unsatisfactory results. Specifically, airborne debris becomes imbedded in the film thus generating noise as the film moves in the housing of the HVAC system. Additionally, after the film was exposed to heat, the edges curled and frayed therefore rendering the film unusable.
In yet another attempt to overcome the aforementioned disadvantages of prior art control surfaces, composite structures designed for use in non-automotive industries were also researched and tested as films in the housing of the HVAC system. Examples of such composite structures include a helium barrier developed by Mann Industries, a division of Takata Global Group of Tokyo, Japan, and two coated woven surfaces disclosed in the U.S. Pat. No. 5,230,937 to Effenberger and in U.S. patent application No. 2001/0034170 to Keese.
The helium barrier developed by Mann Industries includes a 70 denier polyester plain weave fabric sandwiched between two polyurethane primer layers. Further, a polyurethane film layer is disposed on a first face of one of the polyurethane primer layers. Specifically, the helium barrier does not include a silicone topcoat layer disposed on an elastomeric layer.
When tested, the 70 denier fabric did not have sufficient structural rigidity to keep the helium barrier from curling after exposure to high temperatures. In an attempt to overcome the curling of the composite structure, 75 and 150 denier polyester fabrics were substituted in the aforementioned helium barrier and evaluated. When exposed to high temperatures, the 75-denier fabric also exhibited a tendency to curl. Conversely, the 150-denier fabric, when exposed to high temperatures, did not curl.
Additionally, testing also showed that when the helium barrier was placed in the housing of the HVAC system airborne debris became imbedded in the polyurethane primer layer. As the helium barrier was moved within the housing of the HVAC system, the imbedded airborne debris generated unacceptable noise. Yet, the airborne debris did not imbed in the polyurethane film layer.
In an attempt to remedy the noise generation, the polyurethane film layer was disposed on a face of both polyurethane primer layers in the aforementioned helium barrier. Although this construction of the helium barrier minimized noise generation, the helium barrier was found to adhere to itself. Additionally, the helium barrier was found to exhibit a high coefficient of friction when moved within the housing of the HVAC system. Further, diatomaceous earth was added to the film in an attempt to reduce the film's tendency to adhere to itself. Yet, this had no positive effect.
As an alternative to the helium barrier developed by Mann Industries, the Effenberger patent discloses a composite structure including a substrate that is unlike the helium barrier. The substrate is preferably a textile substrate, coated on one or both faces with a matrix. The matrix includes an initial perfluoropolymer layer and a fluoroelastomer overcoat layer. In some embodiments, a methylphenyl silicone oil is also added to the matrix. More specifically, the Effenberger patent does not disclose a composite structure that includes a silicone topcoat disposed on an elastomeric layer.
In a first embodiment of the Effenberger patent, a perfluorinated polymer is disposed, as an initial layer, on one or both faces of the substrate. Additionally, a fluoroelastomer layer is disposed, as an overcoat layer, on the initial perfluoropolymer layer.
In a second embodiment of the Effenberger patent, the methylphenyl silicone oil is applied simultaneously with the perfluoropolymer thus forming a mixed perfluoropolymer layer disposed on the substrate. In a third embodiment of the Effenberger patent, the methylphenyl silicone oil is applied to the substrate first, followed by an application of the perfluoropolymer, thus resulting in a methylphenyl silicone oil layer sandwiched between the perfluoropolymer layer and the substrate. Additionally, in all of the aforementioned embodiments, multiple fluoroelastomer layers may be added as topcoat layers, if so desired.
Specifically, the substrate of the Effenberger patent may include glass, fiberglass, ceramics, graphite, polybenzimidazole, polyaramides, polytetrafluoroethylene, metal, polyolefins, polyesters, polyamides, copolymers of tetrafluoroethylene, polyether sulfones, polyimides, polyether ketones, polyetherimides, novoloid phenolic fibers or natural textiles. The initial perfluoropolymer layer and the overcoat fluoroelastomer layer include polytetrafluoroethylene, ethylene-propylene copolymers, or copolymers of tetrafluoroethylene and perfluoro-propyl vinyl ether.
The Keese application discloses a substrate that is also unlike the helium barrier developed by Mann Industries. The Keese application discloses a substrate and a perfluoropolymer layer disposed on a first and second face of the substrate. Additionally, a colloidal silica dispersion and a perfluorinated copolymer resin dispersion are disposed on the second face of the substrate to render the surface bondable. Finally, an elastomeric layer is disposed on the colloidal silica dispersion and the perfluorinated copolymer resin dispersion.
More specifically, the substrate is reinforced with glass or fiberglass. Additionally, the perfluoropolymer layer includes polytetrafluoroethylene or other similar compounds. Further, the elastomeric layer includes a silicone rubber. Still further, the perfluorinated copolymer resin dispersion includes fluorinated ethylene propylene or perfluoroalkoxy-modified tetrafluoroethylene. Specifically, the colloidal silica dispersion disposed on the second face of the substrate is not elastomeric. The colloidal silica dispersion is defined as spheres of silica dispersed in an alkaline medium that produce a negative charge. Finally, the Keese application does not disclose a silicone topcoat layer disposed on the top of the elastomeric layer.
When tested, both the Effenberger and Keese composite structures also yielded unsatisfactory results. Specifically, the perfluoropolymer layer and the elastomeric layer of the composite structures accumulated static charge thus allowing airborne debris to become lodged on the surfaces of the perfluoropolymer layer and the elastomeric layer. This resulted in unacceptable noise as the composite structures were moved between open and closed positions within the housing of the HVAC system.
Further, the elastomeric layer of the composite structure of Keese yielded a tacky surface with a high coefficient of friction. The high coefficient of friction prevented the composite structure from being moved between open and closed positions within the housing of the HVAC system when the elastomeric layer was in contact with the housing of the HVAC system. Additionally, the tacky surface contributed to airborne debris becoming lodged on the tacky surface resulting in unacceptable noise as the composite structures were moved between open and closed positions within the housing of the HVAC system. Still further, as the surface made and broke contact with the rollers, unacceptable noise was generated.
Although the prior art composite structures are currently used in various applications, there remains an opportunity for the development of a composite surface that exhibits superior longevity and physical properties to be used as a film in HVAC systems of motor vehicles.